Self-Assembling Polymer Creates Square Microchips

Scientists at the Massachusetts Institute of Technology (MIT) have developed a way to manipulate polymers so that they self-assemble into microchips that are square or rectangular, a shape that is much better than current hexagonal shapes, because they can lead to more densely arranged components.

The MIT researchers’ method guides self-assembling molecules to produce wires with right angles or curves. They use a template array of tiny posts on a surface of a substrate to guide the pattern of polymer molecules. The forces acting between those molecules make them arrange themselves in a specific way, reports The Engineer.

The template is coated with a substance that repels one of the polymer components, creating strain on the molecular pattern, says Karl Berggren, associate professor of electrical engineering at MIT. He is co-author of the paper on the research, due to be published in August in the journal, Advanced Materials.

“The polymer then twists and turns to try to avoid this strain, and in so doing rearranges on the surface,” Berggren says in a press release from MIT. “So we can defeat the polymer’s natural inclinations, and make it create much more interesting patterns.”

Self-assembling polymers tend to naturally create hexagonal or a honeycomb patterns, says Caroline Ross, Toyota professor of materials science and engineering, and another author of the paper. “But that’s not what circuit designers want,” she says. “They want patterns with 90 degree angles.”

The development not only creates squares and rectangles, but it also can create cylinders, spheres, ellipsoids, and double cylinders. “You can generate this astounding array of features with a very simple template,” Ross says.

The method also produces arrays of holes that are more tightly packed together than those created with conventional chip-making methods. This means the method can produce microchips with more densely arranged components.

The technique produces multiple, complex shapes simultaneously and in fewer steps than conventional methods. This advantage reduces the time needed to manufacture the chips. It can take several days, or even several months, using electron-beam lithography to create a large area of complex circuitry. The MIT researchers claim that their method could be used as a master pattern to stamp a coating on chips in a more rapid fabrication process.

“There is a growing need and requirement for industry to find an alternative to traditional  photolithography for the fabrication of cutting-edge microelectronic devices,” says Craig Hawker, professor of chemistry and biochemistry at the University of California at Santa Barbara, who was not involved in the work. “This work represents a pivotal achievement in this area and clearly demonstrates that structures once considered impossible to achieve by a self-assembly strategy can now be prepared with a high degree of fidelity.”

Source: “Reseachers build microchips using self-assembling polymers,” The Engineer, 7/19/12
Source: “Research update: Chips with self-assembling rectangles,” MIT press release, 7/19/12
Image by Zephyris, used under its Creative Commons license.